Method of preventing damage of sterile wraps using a tray liner including a foam layer and a paper layer

ABSTRACT

The present invention is directed to a two-ply absorbent liner for use in a sterilization process and, more particularly, to an absorbent liner having a foam layer and a paper layer for cushioning sterilization trays and surgical instruments in a sterilization pack and providing advantageous moisture absorption functionality during and after completion of a sterilization process. The absorbent liner functions advantageously with steam or ethylene oxide gas as the sterilization agent. The absorbent liner is fabricated from a foam material, preferably a hydrophilic polymeric foam material, e.g., a hydrophilic polyurethane foam flame laminated to paper, preferably medical grade paper. The disclosed liner may be advantageously utilized in sterilizing surgical instruments and in conjunction with sterilizing trays such that potential residual moisture is eliminated from the surface of the instruments or trays and metal surfaces are cushioned.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/161,688, filed Mar. 19, 2009, the contents ofwhich is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to liners such as tray liners for use in asterilization process, and more particularly to an absorbent two-plyliner providing an advantageous moisture absorption functionality duringand after completion of a sterilization process. The liner may be usedas a base pad, a tray corner guard, or for cushioning of surgicalinstruments during and after the sterilization process.

BACKGROUND OF THE INVENTION

As is well known, surgical instruments used in the healthcare industrymust be sterilized before and/or after each use. Sterilization, ofcourse, frees instruments from microorganism contamination, to preventinfections and the spread of diseases among patients. All medicalprocedures rely upon a stringent program of sterilization.

The medical device industry has addressed the sterilization requirementsin the surgical field by offering two general types of surgicalinstruments: reusable instruments and single use, or disposable,instruments. Reusable instruments are typically composed of stainlesssteel and are typically sterilized before their initial use and thencleaned and resterilized prior to each subsequent use thereof. Singleuse or disposable instruments, on the other hand, are often fabricatedprimarily from plastic materials, thereby reducing costs associated withmanufacture, and are discarded after use in a single procedure.

With respect to reusable surgical instruments, e.g., forceps, graspers,dissectors, probes, hemostats, scissors and the like, sterilization andresterilization had historically been accomplished using varioussterilization modalities. In a broad sense, these sterilizationprocesses generally involve placing instruments to be sterilized in atray, wrapping the instruments and the tray with a sterilization wrap,and placing the wrapped tray and instruments in a sterilization chamber,where the instruments are exposed to a sterilization medium. In order toprotect the instruments, a tray liner is typically placed on the tray,and then the surgical instruments are placed on the tray liner. In orderto protect the tray itself, the tray is typically placed on cornerguards or a base pad before it is wrapped and placed in thesterilization chamber.

One long and continuing problem encountered with sterilization, however,is the presence of moisture that remains on the sterilized instruments,i.e., within the sterile wrap, at the conclusion of the sterilizationprocess. This residual moisture can range from slight levels of dampnessto visible droplets on the surface of surgical instruments. Suchresidual moisture is both undesirable and is unacceptable because suchmoisture could permit migration of surface microorganisms, therebypenetrating the wrapped tray or basin and rendering its contentscontaminated, and/or may cause rust or pitting of the surgicalinstruments. Also, the wrapped tray may become stained duringsterilization or even torn during loading or removal from asterilization chamber because of the damp condition of the sterilizationwrap.

Tray liners formed of a single material, such as open or closed cellfoam or a cellulose based material have been employed in the past. Forexample, a hydrophilic polyurethane foam trayliner is disclosed in U.S.Pat. No. 6,902,712, incorporated herein by reference. This tray liner iscomprised of a single foam layer. While effective, the evaporation rateand dispersing properties of foam liners could be improved to allow formore efficient moisture absorption and multiple applications within in asterilization system.

Two-ply liners comprised of foam backing are known in the art. Typicallya foam layer is adhered to plastic or cloth. However, use of adhesive tojoin liners used for sterilization presents several problems. Theadhesive may deteriorate when exposed to high heat, steam and/or variouschemicals used in the sterilization process. The liners may delaminateor adhesive may come in contact with the sterile instruments orsterilizing equipment. The adhesive residue is often sticky anddifficult to eliminate.

In addition, laminated paper products which contain at least one layerof paper bonded to a foam layer have also been known for some time. Seee.g. U.S. Pat. Nos. 3,687,797; 3,285,800; 3,530,030; 3,366,532. However,these multi-layered products are also adhered together with an adhesiveor thermally fused with hot rollers. U.S. Pat. No. 4,276,339 discloses amore efficient lamination process via a gelling process; however it doesnot allow the paper and foam to be separately purchased.

A two-ply liner comprised of foam and paper joined by flame laminationhas never been taught for the purpose moisture trapping, and morespecifically for use in sterilization of surgical instruments.

SUMMARY OF THE INVENTION

The present invention is intended to obviate many of the problemsassociated with moisture remaining on or in the trays after asterilization process. Rather than employing a tray liner formed of asingle material, such as open or closed cell foam or a cellulose basedmaterial, as has been done in the past, the present invention employs atwo-ply construction to provide padding as well as absorption. Morespecifically, the present invention combines the cushioning propertiesof foam with the absorbent properties of medical grade paper in order toprotect delicate instruments from impact damage as well as preventingthe adverse effects of moisture, and also to trap moisture and provideprotection when used as a base pad or corner guard.

As exemplified in the Figures and described in detail herein, when usedas a tray liner, it has been found that positioning the inventivematerial with the foam layer adjacent to instruments, such that theinstruments are in contact with the foam layer, provides excellentresults. The instruments are well-protected and the moisture is retainedin the paper layer, away from the instruments, where it spreads outthrough the paper in order to increase the surface area of the moistureand also thereby increase the rate of evaporation.

When used as a base pad or corner guard, it has been found thatpositioning the inventive material with the paper layer adjacent to thetray, such that the tray is in contact with the paper layer, providesexcellent results. The tray is well-protected, and the moisture istrapped in the paper layer before it reaches the sterile wrap. Alsoagain, the moisture spreads out through the paper in order to increasethe surface area of the moisture and also thereby increase the rate ofevaporation.

The inventive material may employ any of numerous types of foammaterial, although polyester polyurethane foam has exhibited excellentresults. The inventive material may also employ any of numerous types ofmedical grade paper, as well.

The foam layer and the paper layer are joined together using a flamelamination technique. As is known, such a technique involves passing thefoam layer through an open flame, thereby creating a thin layer of hotpolymer. The hot polymer is then used as an adhesive to bond the foamlayer to the paper layer to create the inventive material. By employingthis method, excellent results are achieved without the need for aseparate adhesive, the use of which may have its own disadvantages.

BRIEF DESCRIPTION OF THE DRAWINGS

So that those having ordinary skill in the art to which the disclosedliner and associated methods pertain will more readily understand how toemploy and use the same, reference may be had to the drawings wherein:

FIG. 1. is a perspective view of a two-ply liner according to thepresent invention;

FIG. 2 depicts a perspective view of a sterilization system havingvarious placements of an absorbent two-ply liner of the invention;

FIG. 3 is a perspective view of a tray liner according to the presentinvention, lying beneath surgical instruments;

FIG. 4 is a perspective view of a two-ply liner according to the presentinvention, lying beneath surgical instruments and lying below asterilization tray;

FIG. 5 is an alternate perspective view of tray liners according to thepresent invention;

FIG. 6 is a perspective view of a corner guard according to the presentinvention;

FIG. 7 is a perspective view of a corner guard according to the presentinvention positioned on the sterilization tray of FIG. 4;

FIG. 8 is top-down view of a cross section of a corner guard accordingto the present invention positioned on the sterilization tray of FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1 and 5, a two-ply liner of the present invention isillustrated. In particular, an absorbent liner 16 is provided forintroduction into a sterilizing system in connection with thesterilizing process. Liner 16 is composed of two layers 11 and 12. Apaper layer 11 is composed of any type of paper that will allow moistureto be absorbed and dissipate. However, medical grade paper is preferredfor use in sterilization systems. A foam layer 12 is preferablyfabricated from hydrophilic polyurethane foam that is adapted for use insterilization processes that utilize steam or ethylene oxide as thesterilizing agent.

The foam layer 12 is joined to the paper layer 11 at interface 14through flame lamination. Flame lamination overcomes problems of theadhesives of the prior art. First, flame lamination does not have atendency to delaminate when exposed to high temperatures, such as thoseused in the sterilization process. Flame lamination also preventsadhesive from leaking onto or contacting a tray or sterile instrumentsand consequently leaving an undesirable residue.

As shown, absorbent liner 16 is of rectangular configuration; however,alternative geometries are contemplated, e.g., as may be appropriate forspecific sterilization tray configurations. Absorbent tray liners 16 maybe dimensioned depending upon the application. Preferred absorbentliners 16 measure 9 to 15 inches in width and 0.1 inches to 1 inch inthickness. More preferred absorbent liners 16 measure 9, 12 or 15 inchesin width, and are approximately ⅛ inch in thickness. Tray liner 16preferred for use in separating basins measures 3×24 inches and may alsobe ⅛ inch in thickness.

The liner 16 may also be supplied in roll form as depicted in FIG. 5.When provided as a continuous roll, a length of 35 to 40 feet ispreferred.

The liner 16 may, optionally, contain perforations 13. Latitudinalperforations 13 a and longitudinal perforations 13 b may be provided.The latitudinal perforations 13 a allow the liner 16 to sit flatly on asurface since it has a tendency to curl. Moreover, the latitudinalperforations 13 a allow the liner to be torn off a continuous roll, asdepicted in FIG. 5. The latitudinal perforations 13 a may be placed atany suitable interval so that the length of the liner can be chosen toaccommodate sterilization trays of different sizes. Preferably theperforations 13 are about 2 to 3 inches apart. Most preferably, thelatitudinal perforations 13 a are spaced about 2 inches apart.

The liner 16 may also, optionally, contain surface cuts 15 in the paperlayer 11 for purposes of corner relief, as discussed in more detailbelow. The cuts 15 are placed into the paper layer by any suitablemeans.

The absorbent liner 16 of the present invention is particularly adaptedfor use in a steam sterilization system or ethylene oxide sterilizationsystem. As is known, sterilization systems generally include asterilization chamber that is adapted to receive instruments to besterilized, and a source of sterilizing agent, e.g. steam or ethyleneoxide, connected to the sterilization chamber.

Preferably, the absorbent liner 16 is fabricated from a non-woven, lintfree material that is compatible with both steam and ethylene oxidesterilization. The absorbent liner 16 is preferably fabricated from ahydrophilic polymeric foam plastic, e.g. a hydrophilic polyurethane foamthat is clickable.

Typical physical properties of the foam include the following:

Physical Properties Minimum Average Density (lbs./ft³) 1.60 ± 10%Tensile strength (psi) 17.0 25.0 Elongation (%) 80 120 Tear resistance(pli) 1.20 1.90 Compression force Deflection (psi) 25% Deflection 0.600.85 50% Deflection 0.70 0.95 Retention of Tensile Strength afterMinimum 70 3 hours, 105° C., steam autoclave (%) Retention of TensileStrength after Minimum 70 22 hours, 140° C., dry heat aging (%)

With reference to FIGS. 2, 3 and 4, a first embodiment of an absorbentliner 16 of the present invention is illustrated as a tray liner. Theabsorbent tray liner 16 of the present embodiment advantageouslyfunctions to prevent the presence of residual moisture on the surface ofsurgical instruments 20 at the conclusion of the sterilization processby absorbing such potential residual moisture. The surgical instruments20 are positioned adjacent to the foam layer 12. Since the paper layer11 is not adjacent to the surgical instruments, but rather below thefoam layer 12, it pulls moisture from the foam layer 12 and retains anyresidual moisture. The moisture is free to spread out through the paperto increase the surface area of the moisture and thereby increase therate of evaporation. Thus, the foam layer 12 advantageously cushionssurgical instruments to be sterilized, e.g., forceps, graspers,dissectors, probes, hemostats, scissors and the like, both during andafter the sterilization process and will not leave residual moisture onsurgical instruments 20.

With reference to FIGS. 2 and 3, absorbent tray liner 16 generallycomprises a sheet of absorbent material cut to substantially cover abase 32 of a sterilization tray 30. The base 32 of the sterilizationtray 30 may be solid or perforated, as is known in the art.

FIG. 4 shows a second embodiment of an absorbent liner 16 of the presentinvention as a base pad. The absorbent liner 16 of the base padembodiment advantageously functions to pull and retain moisture awayfrom wrap 40 during and at the conclusion of the sterilization processby absorbing such potential and residual moisture. The paper layer 11 ispositioned underneath and adjacent to the tray 30. The paper layer pullsmoisture away from the wrap 40 and retains any residual moisture towardthe tray 30. The moisture is free to spread out through the paper toincrease the surface area of the moisture and thereby increase the rateof evaporation. The foam layer 12 advantageously cushions the tray andprotects any sterilization wrap 40 or cart that may be used.

A method for sterilizing instruments 20 according to the presentinvention includes positioning the tray liner 16 in the base of the tray30 such that the paper layer 11 is adjacent to the tray base 32 andpositioning instruments on the foam layer 12. The types of instruments20 that may benefit from sterilization method disclosed herein includeall conventional surgical instruments composed of stainless steel.Determinations as to the types of surgical instruments to be placed onthe tray 30, the numbers/weights of such surgical instruments,sterilization cycles, and the like, are made according to conventionalsterilization criteria.

Tray 30 is then advantageously wrapped in a conventional sterilizationwrap 40. Sterilization wrap 40 may be fabricated from paper and,optionally, a second absorbent tray liner 16 or other cushioning membermay be placed between tray 30 and sterilization wrap as a base pad,thereby reducing the risk that wrap 40 may be torn by the corners oftray 30. Once wrapped in the sterilization wrap 40, tray 30 is ready tobe placed in a sterilization unit for sterilization of surgicalinstruments 20. At the conclusion of the sterilization cycle, tray 30 istypically removed from the sterilization unit (not pictured), and thesterilized instruments 20 are, in due course, removed from the tray andmade ready for subsequent surgical procedures. At the conclusion of thesterilization cycle, the absorbent tray liner 16 of the presentinvention is typically disposed of in a conventional waste container.

A preferred method for sterilizing instruments 20 according to thepresent invention includes positioning the liner 16 underneath the outerbase of the tray 30 such that the paper layer 11 is adjacent to the traybase 32 and the foam layer 12 is not in contact with the tray 30. Assuch, the foam layer 12 may contact a sterilization wrap 40, ifutilized. The paper layer 11 will absorb moisture that leaks throughperforations in the base 32 of the tray 30. The paper layer 11 may alsocollect moisture that accumulates on the tray 30 surfaces. Moisture fromthe tray 30 or base 32 will be absorbed by the paper layer 11 anddissipate throughout its surface keeping the foam layer 12 appreciablydry, and in turn keeping sterilization wrap 40 dry and uncompromised.

With reference to FIG. 4, in a particularly preferred method where theliner 16 functions as a base pad, the perforations 13 are adapted tomeet the tray 30 edges. This allows the edges of the liner 16 to befolded upward so that paper layer 11 is adjacent and in contact with theface 33 of the tray 30. This method allows for cushioning and moistureabsorption from the face 33 of the tray as well as the base 32. Moisturefrom the tray 30 will be absorbed by the paper layer 11 and dissipatethroughout its surface keeping the foam layer 12 appreciably dry, and inturn keeping sterilization wrap 40 dry and uncompromised.

Corner relief is provided through the perforations 13. The intersectionof the longitudinal perforations 13 a and the latitudinal perforations13 b may provide a corner box 17 within a sheet of liner 16. The cornerbox 17 may be easily removed through means of the perforations. Once thecorner box 17 is removed, the sides of the liner 16 are more easilyfolded up and positioned adjacent to the tray face 33.

For additional corner relief, the liner of the invention may be providedwith surface cuts 15. Various size cuts 15 are embodied. The surfacescuts 15 are positioned to accommodate the edges of a sterilization tray30, and most preferably the corners of the tray 30. The cuts 15 alsoallow for stabilization of a tray 30 while seated on the liner 16.

The absorbent tray liner of the present invention provides significantbenefits to the reliability and efficacy of conventional sterilizationoperations. Ideally, as is known in the art, when the sterilizationsystem is operating at peak performance a sterilization system thatutilizes steam or ethylene oxide as the sterilizing agent will betotally dry at the conclusion of the sterilization cycle. However, asdiscussed above due to ambient humidity, plumbing, etc., sterilizationsystems are highly variable in operation and such systems do not alwaysoperate at peak levels. As a result, without use of an absorbent trayliner, it is not uncommon for residual moisture to be found on thesurface of sterilized instruments or the sterilization tray at theconclusion of the sterilization cycle. The absorbent tray liner of thepresent invention exhibits sufficient hydrophilicity to absorb an amountof moisture sufficient to address typical operative variability.

The present invention, therefore, provides an absorbent liner 16 thatfunctions to cushion trays and surgical instruments in connection withthe sterilization process, and further functions to absorb potentialexcess moisture that might remain on the surgical instruments or on thetray at the conclusion of a steam or ethylene oxide sterilizationprocess. The absorbent liner has been found to permit proper airremoval, sterilant penetration/evacuation, and delivery of sterilizedsurgical instruments substantially devoid of residual moisture at theconclusion of a sterilization process. The absorbent tray liner has alsobeen found to permit effective aeration of instruments sterilized withethylene oxide.

Another embodiment of the liner in accordance with the present inventionis illustrated in FIGS. 6-8. In particular, a corner guard 50 isprovided which is preferably composed of a polyurethane foam layer 12and a paper layer 11 as described above in connection with the liner 16.In addition, the corner guard is dimensioned for use with asterilization tray such as that shown in FIGS. 2 and 4.

As shown in FIG. 6, guard 50 contains a cavity 51 that is shaped toaccommodate the corner of tray 30. The paper layer 11 is exposed on thesurface of the cavity 51. The outer surface of the guard 50 is comprisedof foam layer 12.

Referring now to FIGS. 7 and 8, the guard 50 is positioned adjacent tothe surface 33 of tray 30 is such that the paper layer 11 is adjacent tothe surface 33. The corner guard 50 advantageously absorbs liquid whileallowing the passage of the sterilization medium therethrough. Themoisture is free to spread out through the paper to increase the surfacearea of the moisture and thereby increase the rate of evaporation. Thus,moisture is retained in the paper layer 11 before it reaches a sterilewrap or cart. Additionally, cushioning and protection are provided forthe tray 30 and penetration of sterilization wrap by sharp corners isprevented.

The principles, preferred embodiments and modes of operation of thepresently disclosed absorbent liners, corner guards and methods ofsterilizing surgical instruments have been described in the foregoingspecification. The presently disclosed absorbent liners and methods ofsterilization, however, are not to be construed as limited to theparticular embodiments shown as these embodiments are regarded asillustrious rather than restrictive. Moreover, variations and changesmay be made by those skilled in the art without departing from thespirit of the presently disclosed absorbent liners, guards and methodsof sterilization.

What is claimed is:
 1. A method of preventing damage of sterile wrapscaused by excessive moisture and rips and tears caused by impact in asterilization system for surgical instruments comprising: providing atray; providing a tray liner having a foam layer fabricated fromabsorbent hydrophilic polymer and a paper layer joined to the foamlayer; positioning said paper layer below and adjacent to said tray;contacting said tray with said paper layer; and wrapping a sterile wraparound said tray and tray liner.
 2. The method of claim 1 wherein thepolymer is polyester polyurethane foam.
 3. The method of claim 1 whereinthe paper is medical grade paper.
 4. The method of claim 1 whereinthickness of the liner is between 0.1 inches to 1 inch.
 5. The method ofclaim 4 wherein the thickness is about ⅛ of an inch.
 6. The method ofclaim 1 wherein the liner width is between 9 inches and 15 inches.
 7. Amethod of preventing damage of sterile wraps caused by excessivemoisture and rips and tears caused by impact in a sterilization systemfor surgical instruments comprising: providing a tray having traycorners; providing a tray liner having a foam layer fabricated fromabsorbent hydrophilic polymer and a paper layer joined to the foamlayer; positioning said foam layer adjacent to a tray corner; contactingsaid tray corner with said paper layer; and wrapping a sterile wraparound said tray and tray liner.